Practical steam engine

ABSTRACT

The current invention is a high speed, two-stroke engine that is counter flow, semi-uniflow, or uniflow and is comprised of at least one variable rotary valve mechanism.

CROSS-REFERENCES TO RELATED APPLICATIONS

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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

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BACKGROUND OF INVENTION

Low grade fuels (low density, low heating value solid, liquid and gaseous substances) are not competitive with higher grade commercial fuels in small scale (e.g., less than 2000 kW) mobile and stationary power plants. This is mainly due to the lack of small scale, efficient, low cost steam prime movers that can economically convert low grade fuels into usable, industrial power.

The traditional reciprocating steam engine, in its various forms, has become economically and technologically obsolete due to the availability of refined, petroleum based fuels that were better utilized in more efficient heat engine cycles (Otto, Diesel and Brayton cycles) and the development of low cost electrical power delivered by the interconnected utility power grid. The traditional steam engine is limited by its ability to convert raw, unrefined fuel sources into clean, high quality steam energy that is converted to mechanical work. The final evolution of reciprocating steam engine technology circa 1950 is represented by the uniflow steam engine. The first American uniflow engine was built in 1913 by the Skinner Engine Company of Erie, Pa.; the last one was built in 1982. The Skinner Engine Company closed its doors and was liquidated in 2003.

The Skinner Universal Uniflow steam engine, circa 1950, represents the current state of the art for commercially manufactured, industrial steam engines applied to stationary service. The Skinner Uniflow steam engine was a major improvement over previous engine types because it improved steam flow dynamics and thermal efficiency. But it could only work at relatively low speeds (e.g., generally not exceeding 400 rpm). Thus, it required high torque outputs. The result is that the Skinner Uniflow engine had five major weaknesses: (a) massive and costly components that could not withstand high reaction forces generated by large piston diameters due to low rotational speeds (generally not above 400 rpm); (b) double acting pistons required complex piston rod/crosshead/connecting rod assemblies that limited rotational speeds due to high inertia forces that could not be adequately balanced at high speed; (c) long cutoffs of up to 40% that adversely impacted thermodynamic performance; (d) need for large concrete foundations to support the heavy engine weights and separate condenser, and, therefore, lack of portability; and (e) higher cost compared to less efficient steam turbines due to higher manufacturing and labor costs.

A compact, thermodynamically and power efficient steam engine that runs at higher speeds, and therefore, requires lower torque outputs, has smaller components and does not require a massive support foundation is unknown in the prior art.

SUMMARY OF INVENTION

The present invention is directed to a Practical Steam Engine that can run at higher speeds (at least 400 rpms) and, thus, requires lower torque outputs. This lower torque output, in turn, allows the power delivery through smaller components that do not need to be supported by a massive concrete foundation as does the prior art uniflow engine. The fact that the Practical Steam Engine can be made compactly and relatively portable makes it ideal for off-grid power generation applications. The Practical Steam Engine may be fueled by biomass, such as slash and thinnings as part of forest management practices, or for providing steam-generated power at a merchantable timber source to add value to wood product processes.

The Practical Steam Engine includes at least one cylinder head assembly, an admission and exhaust valve assembly, a cylinder/piston assembly, a crank shaft assembly or other similar apparatus that converts between reciprocating motion and rotational motion, a valve gear assembly. The admission or the exhaust valve assembly, or both the admission and exhaust valve assembly includes a variable duration, rotary valve (the “rotary valve”). The rotary valve eliminates reciprocating motion reducing the number of moving components therefore reducing the failure rate of mechanical components. Another advantage of the rotary valve is that it, in its typical motion, does not move in a direction significantly affected by the forces of net pressure forces of the working fluid, a common problem experienced by poppet-valves and slide valves conventionally used in these types of engines.

When the Practical Steam Engine is placed into a conventional Rankine cycle with an evaporator (boiler), condenser, and pumps, the overall energy generation plant may produce mechanical work using raw, unrefined fuel sources such as biomass (e.g., residual forest waste) and other unconventional fuel sources, as well as conventional fuel sources. The Practical Steam Engine steam-powered generator is more compact in size than prior art. For example, The Practical Steam Engine may, for example, be transported to remote areas, particularly where remotely-accessed biomass may be located. This cuts down on the high cost and pollution from using conventional fuel sources (e.g., Diesel oil) to transport the biomass to the Practical Steam Generator. This compact-size steam generator using the Practical Steam Engine can be utilized within deep forests as part of forestry management or at a merchantable timber source to allow value-added processing at or closer to the power source (such as at sawmills, or wood palletizing and pulp chipping). Further, the Practical Steam Engine may be used to produce higher value wood processed products closer to the power source, thereby reducing transportation logistics, costs and additional carbon emissions from such transportation.

The single acting, simple expansion design of the Practical Steam Engine lends itself to conversion of a counter flow, semi-uniflow or uniflow engine to a counter flow, semi-uniflow, or uniflow engine for steam operation. The conversion process replaces a cylinder head, including the poppet valves, of a conventional engine with a cylinder head having an integral valve assembly. The resulting converted engine to steam engine operates at high volumetric efficiency.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed descriptions of the preferred embodiment with reference to the accompanying drawings, of which:

FIG. 1 is an isometric view of an exemplary counterflow engine;

FIG. 2 is an isometric view of an exemplary semi-uniflow engine

FIG. 3 is an isometric view of an exemplary uniflow engine;

FIG. 4 is a side view of an exemplary counterflow engine;

FIG. 5 is a side view of an exemplary semi-uniflow engine;

FIG. 6 is a side view of an exemplary uniflow engine;

FIG. 7 is a section view of an exemplary counterflow engine (section 1-1) taken from FIG. 4;

FIG. 8 is a section view of an exemplary semi-uniflow engine (section 2-2) taken from FIG. 5;

FIG. 9 is a section view of an exemplary uniflow engine (Section 3-3) taken from FIG. 6;

FIG. 10 is a top view of dual valve head assembly for exemplary counterflow engine and semi-uniflow engine;

FIG. 11 is a top view of single valve head assembly for an exemplary uniflow engine;

FIG. 12 is a section view of intake valve assembly as used in exemplary counterflow engine, semi-uniflow engine and uniflow engine (section 4-4) taken from FIG. 11;

FIG. 13 is a section view of exhaust valve assembly as used in exemplary counterflow engine and semi-uniflow engine (section 5-5) taken from FIG. 10;

FIG. 14 is a section view of cylinder head assembly as used in exemplary counterflow engine and semi-uniflow engine (section 6-6) taken from FIG. 10;

FIG. 15 is a section view of cylinder head assembly as used in an exemplary uniflow engine (section 7-7) taken from FIG. 11;

FIG. 16 is an isometric view of intake valve assembly as used in exemplary counterflow engine, semi-uniflow engine and uniflow engine;

FIG. 17 is an isometric view of exhaust valve assembly as used in exemplary counterflow engine and semi-uniflow engine;

FIG. 18 is an isometric view of adjustment valve assembly as used in exemplary counterflow engine, semi-uniflow engine and uniflow engine.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, may be embodied in many different forms and should not be construed as limited to the embodiments set for herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. The current invention is a high speed, two-stroke engine that is counter flow, semi-uniflow, or uniflow and is comprised of at least one variable rotary valve mechanism. Working fluid, referred to herein, may be organic and/or inorganic fluid, naturally occurring and/or man-made. Working fluid may include: Chlorofluorocarbon (CFC) (e.g. R-11, R-12); Hydro-fluorocarbons (HFC) (e.g. R-134a, R-245fa); Hydro-chlorofluorocarbon (HCFC) (e.g. R-22, R-123); Hydrocarbons (HC) (e.g. Butane, methane, pentane, propane, etc.); Perfluocarbon (PFC); Basic organic compounds (Carbon dioxide, etc.); Inorganic compounds (e.g. Ammonia); Elements (Hydrogen, etc.), or a combination thereof, amongst others. A preferred working liquid is water.

Most commercial engines have four, six, or eight cylinders where each cylinder operationally houses a piston. The current invention may have a conventional number of cylinders however; it must have at least one cylinder. Referring to FIGS. 1, 2, 3, for exemplary purposes, the Practical Steam Engine 10 is illustrated as an engine having a single cylinder. Working fluid is distributed to the engine at 35 by an intake rotary valve assembly 22. Referring to FIGS. 1, 4, 7, in a counterflow engine working fluid exits the engine through at least one exhaust port 36 which is regulated by an exhaust rotary valve assembly 24. Referring to FIGS. 2, 5, 8, in a semi-flow engine working fluid exits the engine through at least two exhaust ports 36 and 39. Preferably, the exhaust port 39 exhausts working fluid from at least one cylinder wall exhaust port 40 when the piston 14 travels below the cylinder wall exhaust ports 40. Referring to FIGS. 3, 6, 9, in a uniflow engine working fluid exits the engine through exhaust port 39 from wall port 40 when the piston 14 travels below the cylinder wall exhaust ports 40. In one embodiment, whether a counterflow, semi-uniflow or uniflow type engine, the exhaust from exhaust port (36, 39) may be fed into the working fluid inlet port 35 of another engine or to the working fluid inlet port 35 of another cylinder of a multiple cylinder engine.

Referring to FIGS. 1, 2, 3, preferably, a belt drive system is used to transmit mechanical energy. More specifically, the intake rotary valve assembly 22 and exhaust rotary valve assembly 24 are driven by at least one main power shaft 15. The power shaft 15 may be a crankshaft or similar mechanism that converts between reciprocating motion and rotational motion. Torque is transmitted to the intake drive belt 41 and exhaust drive belt 42 from the power shaft 15 via a primary drive pulley 43. The intake drive belt 41 and exhaust drive belt 42 transmits torque to the intake rotary valve assembly 22 and exhaust rotary valve assembly 24 by through an intake valve pulley 44 and exhaust valve pulley 45. The intake valve pulley 44 and the exhaust valve pulley 45 are operationally attached to the intake rotary valve assembly 22 front end 22 b and exhaust rotary valve assembly 24 front end 24 b, respectively. Alternatively, a chain, gear, hydraulic, electric or other similar system may be used to transmit torque through the system.

Referring to FIGS. 1-6 and 14, and 15, the cylinder head assembly 11 is operationally attached to a cylinder block 12. The cylinder block 12 houses at least one cylinder 13 which is comprised of at least one reciprocating piston 14. The linear motion of the reciprocating piston 14 is converted to rotational movement at the main power shaft 15 by a crank-slider mechanism 17 or other similar mechanism. The crank-slider mechanism 17 is comprised of at least one connecting rod 16 which transmits force between the main power shaft 15 and the reciprocating piston 14.

Referring to FIG. 14, preferably, in a semi-uniflow engine the interior of the cylinder head assembly 11 is comprised of an intake rotary valve assembly cylindrical bore 20, and an exhaust rotary valve assembly cylindrical bore 21. Referring to FIG. 15, preferably, in a uniflow engine the interior of the cylinder head assembly 11 is comprised of an intake rotary valve cylindrical bore 20. Referring to FIG. 14, preferably, in a counter-flow engine the interior of a cylinder head assembly is comprised of an intake rotary valve assembly cylindrical bore 20 and exhaust rotary valve assembly cylindrical bore 21. The inside diameter of the intake rotary valve assembly 22 receives an adjustment valve assembly 23.

Referring to FIG. 18, the adjustment valve assembly 23 is comprised of an adjustment tube 23 a which has an inside diameter 23 d and outside diameter 23 e. Referring to FIGS. 12 and 16, the intake rotary valve assembly 22 is comprised of an intake tube 22 a which runs complimentary along the outside diameter 23 e of the adjustment tube 23 a and the intake rotary valve assembly cylindrical bore 20. The adjustment valve assembly 23 communicates with the intake rotary valve assembly 22 via adjustment valve port 32. The intake rotary valve assembly 22 communicates with the cylinder via intake valve cylinder port 33 and cylinder head intake port 30. Contained within the exhaust valve cylindrical bore 21 is the exhaust rotary valve assembly 24. Referring to FIGS. 13 and 17, the exhaust rotary valve assembly 24 communicates with the cylinder 13 via exhaust tube port 34 and cylinder head exhaust port 31.

Referring to FIGS. 12 and 16, the intake rotary valve assembly 22 is turned by the intake valve assembly 22 front end 22 b which is driven by the power shaft 15 of the engine. The intake valve assembly 22 front end 22 b supports the front of the intake valve tube 22 a and the intake valve assembly 22 rear end 22 c supports the rear of the intake valve tube 22 a. These components are connected together by known fasteners such as bolts, screws, cross pins, amongst others. The intake valve assembly front end 22 b is supported by a bearing 25 operably mounted to the cylinder head assembly 11. Preferably, the bearing 25 is aligned concentrically to the intake rotary valve assembly 22 cylindrical bore 20. Known seals protect the bearings 25 from the working fluid; preferably, the seals are rotary lip seal 26.

The intake rotary valve assembly 22 accommodates the adjustment valve assembly 23. The adjustment valve assembly 22 front end 23 b is supported by a bearing 27 mounted to the intake rotary valve assembly 22 front end 22 b. Similarly, the rear end 23 c of the adjustment valve assembly 23 rear end is supported by a bearing 27 located to the intake valve assembly rear end 22 c. Additionally, a stationary bushing 28 is operably mounted to the cylinder head assembly 11. Preferably, the stationary bushing 28 is aligned concentrically with the intake rotary valve assembly cylindrical bore 20, and supports the rear end 23 a of the adjustment valve assembly 23. Known seals prevent working fluid leakage and protects the valve bearing 25 from the working fluid; preferably, the seal is a rotary lip seals 29.

Working fluid is supplied through the working fluid inlet port 35 and fills the cylinder head annular volume around the intake valve assembly 22. The working fluid travels through working fluid ports 37, radially located around the circumference of the intake valve tube 22 a. As the intake valve assembly 22 rotates, these ports align with adjustment tube working fluid ports 38, radially located around the circumference of the adjustment valve tube 23 a, thus supplying working fluid to the interior of the adjustment valve tube 23 a. When the intake valve cylinder ports 33 and adjustment valve cylinder ports 32 align as described in FIG. 7, the working fluid is admitted to the cylinder. The adjustment valve angular position, as described in FIG. 7, may be varied by providing external rotational force to the adjustment valve rear end 23 c on the shaft protruding from the rear of the cylinder head assembly.

Referring to FIGS. 13 and 17, the exhaust valve assembly front end 24 b supports the front of the exhaust valve tube 24 a and the exhaust valve assembly rear end 24 c supports the rear of the exhaust valve tube 24 a. These components are operably connected by known fasteners such as whether bolts, screws, cross pins, amongst others. The exhaust valve assembly front shaft is supported by a bearing 25 mounted to the cylinder head assembly 11, located concentrically to the exhaust rotary valve assembly cylindrical bore 21. Preferably, the exhaust valve assembly front shaft is supported by a bearing 25 mounted to the cylinder head assembly 11, located precisely concentrically to the exhaust rotary valve assembly cylindrical bore 21. Any known seal can protect the bearing 25 from the working fluid; preferably, rotary lip seals 26 are used.

Once exhaust working fluid leaves the cylinder 13 and is delivered to the interior of the exhaust valve tube 24 a through the exhaust tube port 34, the exhaust rotary valve assembly 24 rotates until the exhaust tube port 34 aligns with the primary exhaust port 36. The intake rotary valve assembly 22 rotates at a speed directly related to the engine speed. The intake rotary valve assembly 22 may rotate at the same speed of the engine, one-half the engine speed, one-third of the engine speed, etc. Preferably, the intake rotary valve assembly 22 rotates at one-half engine speed. When the working fluid inlet port 38 aligns with the cylinder head intake port 30 and the adjustment valve cylinder port 32, working fluid is allowed into the interior of the adjustment valve tube 23 a to be supplied to the cylinder 13 via the cylinder head intake port 30.

The adjustment valve assembly 23 may be adjusted angularly by rotating the adjustment valve assembly 23 rear end 23 c by adjusting the duration of communication between the interior of the adjustment valve tube 23 a and the cylinder head intake port 30, resulting in control of admission cutoff. The control of this admission cutoff may be used to control engine speed and/or power output. The exhaust valve tube 24 a also rotates at a speed directly related to engine speed. The exhaust rotary valve assembly 24 may rotate at the same speed of the engine, one-half the engine speed, one-third of the engine speed, etc. Preferably the exhaust rotary valve assembly 24 rotates one-half the speed of the engine. As the exhaust valve tube 24 a rotates, the exhaust tube port 34 aligns with the cylinder head exhaust port 31. Working fluid is exhausted from the cylinder 13 into the interior of the exhaust valve tube 24 a. When the exhaust tube port 34 aligns with the primary exhaust port 36, working fluid is exhausted from the interior of the exhaust valve, thus allowing exhaust working fluid to exit the cylinder head assembly 11 and subsequently the engine 10. Preferably, both the intake valve tube 22 a and the exhaust valve tube 24 a may utilize diametrically opposed cylinder ports, thus producing an inherently radially balanced valve. Preferably the intake valve 22 and the exhaust valve 24 operate at precisely one-half engine speed—increasing bearing life.

Referring to FIG. 12, the intake rotary valve assembly 22 is comprised of: an intake valve tube 22 a, a front end 22 b and a rear end 22 c. The front end 22 b and the rear end 22 c are operably connected to the intake valve tube 22 a via known fasteners such as bolts, screws, cross pins, amongst others. The intake valve tube 22 a includes at least one cylinder port 33 and at least one working fluid inlet port 37.

Referring to FIG. 9, the exhaust rotary valve assembly 24 is comprised of: an exhaust valve tube 24 a, a front end 24 b and a rear end 24 c. The front end 24 b and the rear end 24 c are operably connected to the exhaust valve tube 24 a via known fastening methods such as bolts, screws, cross pins, welded, amongst others. The exhaust valve tube 24 a includes at least one tube port 34.

Referring to FIG. 10, the adjustment valve assembly 23 is comprised of the following components: an adjustment valve tube 23 a, a front end 23 b and a rear end 23 c. The front end 24 b and the rear end 24 c are operably connected to the adjustment valve tube 23 a via known fastening methods such as bolts, screws, cross pins, welded, amongst others. The adjustment valve tube 23 a includes at least one cylinder port 32 and at least one working fluid inlet port 38. 

1. A Practical Steam Engine comprising: a cylinder head/valve gear assembly having an inlet to receive working fluid; at least one intake rotary valve assembly, at least one exhaust rotary valve assembly, or a combination thereof; a cylinder/piston assembly with one end of the cylinder/piston assembly adjacent to the cylinder head/valve gear assembly, said cylinder/piston assembly configured to provide in-line movement between a piston and a corresponding cylinder of the cylinder/piston assembly when a source fluid pushes an end of the cylinder/piston assembly; an apparatus that converts linear motion of the piston to rotational movement of the shaft.
 2. The Practical Steam Engine of claim 1 where the intake rotary valve assembly is comprised of: a body; where the body has an opening therein of a circular cross section; where the body has a means to communicate with the opening and is adapted for connection to the source fluid; a first annular member received in the opening; where the first annular member has at least one aperture of fixed circumferential dimension there through positioned to intermittently communicate with the means to communicate upon rotation of the first annular member in the opening; a means to continuously rotating the first annular member in the opening; a second stationary annular member; where the second annular member is received in the first annular member; where the second annular member has at least on means to intermittently communicate with the aperture of the first annular member upon rotation; where the second annular member has a passage means adapted for connection to a source fluid; where the passage means is connected to the means to communicate of the second annular member; a means for adjusting the angular position of the means to communicate in the second annular member relative to the means to communicate in the body independently of the first annular member thereby varying the cutoff of the fluid to the means to communicate in the body upon rotation of the first annular member.
 3. The Practical Steam Engine of claim 2 where the first annular member is supported by at least one bearing; where the second annular member is supported by at least one bearing.
 4. The Practical Steam Engine of claim 1 where the exhaust rotary valve assembly is comprised of: a body; where the body has an opening therein of a circular cross section; where the body has a means to communicate with the opening and is adapted for connection to the source fluid; a first annular member received in the opening; where the first annular member has at least one aperture of fixed circumferential dimension there through positioned to intermittently communicate with the means to communicate upon rotation of the first annular member in the opening; a means to continuously rotating the first annular member in the opening; a second stationary annular member; where the second annular member is received in the first annular member; where the second annular member has at least on means to intermittently communicate with the aperture of the first annular member upon rotation; where the second annular member has a passage means adapted for connection to a source fluid; where the passage means is connected to the means to communicate of the second annular member; a means for adjusting the angular position of the means to communicate in the second annular member relative to the means to communicate in the body independently of the first annular member thereby varying the cutoff of the fluid to the means to communicate in the body upon rotation of the first annular member.
 5. The Practical Steam Engine of claim 4 where the first annular member is supported by at least one bearing; where the second annular member is supported by at least one bearing.
 6. The Practical Steam Engine of claim 1 where exhaust from the exhaust rotary valve assembly is fed into a working fluid inlet port of another engine or a working fluid inlet port of another cylinder of a multiple cylinder engine.
 7. A Practical Steam Engine comprising: a cylinder head/valve gear assembly having an inlet to receive working fluid; at least one intake rotary valve assembly; at least one exhaust port which exhausts through at least one cylinder wall exhaust port; a cylinder/piston assembly with one end of the cylinder/piston assembly adjacent to the cylinder head/valve gear assembly, said cylinder/piston assembly configured to provide in-line movement between a piston and a corresponding cylinder of the cylinder/piston assembly when a source fluid pushes an end of the cylinder/piston assembly; an apparatus that converts linear motion of the piston to rotational movement of the shaft.
 8. The Practical Steam Engine of claim 7 where the intake rotary valve assembly is comprised of: a body; where the body has an opening therein of a circular cross section; where the body has a means to communicate with the opening and is adapted for connection to the source fluid; a first annular member received in the opening; where the first annular member has at least one aperture of fixed circumferential dimension there through positioned to intermittently communicate with the means to communicate upon rotation of the first annular member in the opening; a means to continuously rotating the first annular member in the opening; a second stationary annular member; where the second annular member is received in the first annular member; where the second annular member has at least on means to intermittently communicate with the aperture of the first annular member upon rotation; where the second annular member has a passage means adapted for connection to a source fluid; where the passage means is connected to the means to communicate of the second annular member; a means for adjusting the angular position of the means to communicate in the second annular member relative to the means to communicate in the body independently of the first annular member thereby varying the cutoff of the fluid to the means to communicate in the body upon rotation of the first annular member.
 9. The Practical Steam Engine of claim 8 where the first annular member is supported by at least one bearing; where the second annular member is supported by at least one bearing.
 10. The Practical Steam Engine of claim 7 where exhaust from the cylinder wall exhaust port is fed into a working fluid inlet port of another engine or a working fluid inlet port of another cylinder of a multiple cylinder engine.
 11. A Practical Steam Engine comprising: a cylinder head/valve gear assembly having an inlet to receive working fluid; at least one intake rotary valve assembly, at least one exhaust rotary valve assembly, or a combination thereof; at least one exhaust port which exhaust through at least one cylinder wall exhaust port; a cylinder/piston assembly with one end of the cylinder/piston assembly adjacent to the cylinder head/valve gear assembly, said cylinder/piston assembly configured to provide in-line movement between a piston and a corresponding cylinder of the cylinder/piston assembly when a source fluid pushes an end of the cylinder/piston assembly; an apparatus that converts linear motion of the piston to rotational movement of the shaft.
 12. The Practical Steam Engine of claim 11 where the intake rotary valve assembly is comprised of: a body; where the body has an opening therein of a circular cross section; where the body has a means to communicate with the opening and is adapted for connection to the source fluid; a first annular member received in the opening; where the first annular member has at least one aperture of fixed circumferential dimension there through positioned to intermittently communicate with the means to communicate upon rotation of the first annular member in the opening; a means to continuously rotating the first annular member in the opening; a second stationary annular member; where the second annular member is received in the first annular member; where the second annular member has at least on means to intermittently communicate with the aperture of the first annular member upon rotation; where the second annular member has a passage means adapted for connection to a source fluid; where the passage means is connected to the means to communicate of the second annular member; a means for adjusting the angular position of the means to communicate in the second annular member relative to the means to communicate in the body independently of the first annular member thereby varying the cutoff of the fluid to the means to communicate in the body upon rotation of the first annular member.
 13. The Practical Steam Engine of claim 12 where the first annular member is supported by at least one bearing; where the second annular member is supported by at least one bearing.
 14. The Practical Steam Engine of claim 11 where the exhaust rotary valve assembly is comprised of: a body; where the body has an opening therein of a circular cross section; where the body has a means to communicate with the opening and is adapted for connection to the source fluid; a first annular member received in the opening; where the first annular member has at least one aperture of fixed circumferential dimension there through positioned to intermittently communicate with the means to communicate upon rotation of the first annular member in the opening; a means to continuously rotating the first annular member in the opening; a second stationary annular member; where the second annular member is received in the first annular member; where the second annular member has at least on means to intermittently communicate with the aperture of the first annular member upon rotation; where the second annular member has a passage means adapted for connection to a source fluid; where the passage means is connected to the means to communicate of the second annular member; a means for adjusting the angular position of the means to communicate in the second annular member relative to the means to communicate in the body independently of the first annular member thereby varying the cutoff of the fluid to the means to communicate in the body upon rotation of the first annular member.
 15. The Practical Steam Engine of claim 14 where the first annular member is supported by at least one bearing; where the second annular member is supported by at least one bearing.
 16. The Practical Steam Engine of claim 11 where exhaust from the exhaust rotary valve assembly and/or cylinder wall port is fed into a working fluid inlet port of another engine or a working fluid inlet port of another cylinder of a multiple cylinder engine. 